Various types of planting units for a seeding machine have been developed, many of which use a seed meter that is driven rotationally. In some configurations, the seed meter is driven by a ground wheel on the planting machine mechanically coupled to the seed meter by a shaft extending laterally of the machine with chains or cables connecting the shaft to each seed meter. In other configurations, the cross shaft may be coupled to a motor for rotation instead of the ground wheel. In other configurations of planting units, the seed meters may be separately driven by motors, such as electric, hydraulic or pneumatic. It may be useful to be able to easily de-couple the meter from the drive motor for servicing of the planting unit. Accordingly, a drive coupling between the motor and seed meter that is self-aligning and which is easily coupled and de-coupled is desired.